Hydraulic control system



March 2, 1965 v. A. NELSON HYDRAULIC CONTROL SYSTEM Filed Dec. 4, 1961 RO T N E V m 0 w N 8! E W w V Rule 8 mm mm X United States Patent3,171,496 HYDRAULHC CONTRGL SYSTEM Vaughn A. N elson, Downers Grove,Ill., assignor to International Harvester Company, Chicago, Ill., acorporation of New Jersey Filed Dec. 4, 1961, Ser. No. 156,744- 7Claims. (Cl. 172-9) This invention relates generally to hydraulicsystems. More particularly, it is directed to a hydraulic system for usewith a vehicle such as a tractor in controlling the operation ofimplements associated therewith.

Systems of this type utilize a fluid operated motor for raising andlowering the implement between transport and working positions.Generally, operator responsive means actuates the system for directingfluid to a hydraulic ram in order to move the implement to its raised ortransport position. Fluid is relieved from the hydraulic ram in order tomove the implement to its lowered or working position.

Such systems also utilize the fluid operated motor for adjusting thedraft control of the implement. The system is actuated by additionaloperator responsive means to set the implement at a desired workingdepth. During operation the system is additionally under the control ofcompressive means responsive to a positive or negative load on theimplement as it encounters varying working conditions. This results in acounteracting corrective action on the implement according to conditionsaffecting the draft forces thereon. With the use of high pressuresystems, oversensitive response to load variations results in acorrective action that may become overbalancing and cause undesirableoscillation or chattering of the implement. In addition, the buildup offluid pressure within such a system to a value greater than thatnecessary for actuation of the hydraulic ram may result in excessiveheating of the fluid. Under such conditions serious damage to componentsof the system may be encountered.

Accordingly, it is an object of this invention to provide hydrauliccontrol means for a draft control system which will compensate foroversensing of load variations.

Another object of this invention is to provide hydraulic control meansfor a draft control system incorporating means for delaying the flow offluid to an associated hydraulic ram for a predetermined period in orderto prevent application of pressure in response to momentary loadfluctuations.

Yet another object of this invention is to provide hydraulic controlmeans for a draft control system including valve means operable inresponse to the sensing of variations in draft load for controlling theflow of fluid under high pressure, operation of the valve meansinitiating action of means allowing fluid pressure to build up in thesystem only after the valve means has remained in its operating positionfor a predetermined time so that undesirable chattering of the valvemeans does not cause fluid to flow under high pressure.

Still another object of this invention is to provide valve meansincorporating a control valve for directing the flow of fluid underpressure and a bypass valve actuated by dashpot means which in turn isactuated by the control valve to delay pressure buildup for apredetermined period after operation of the control valve.

An additional object of this invention is to provide valve meansincorporating a control valve for directing the flow of fluid underpressure and a bypass valve actuated by dashpot means which in turn isactuated by the control valve such that failure of the dashpot meansprevents actuation of the bypass valve and buildup of pressure.

A further object of this invention is to provide hydraulic control meansfor a draft control system wherein exces- $121,495 Patented Mar. 2, 1965 sive pressure buildup is prevented, thus avoiding the heatingattendant thereto and damage to system components caused thereby.

A still further object of this invention is to provide valve meansincorporating a control valve for directing the flow of fluid underpressure and a bypass valveactuated by dashpot means which in turn isactuated by the control valve such that the buildup of pressure iscontrolled within' predetermined limits in order to avoid excessiveheating and damage to system components caused thereby.

The foregoing along with additional objects and advantages will beapparent from the following description of a specific embodiment of theinvention as shown in the accompanying drawing, in which the draftsensing means and control linkage means are shown diagrammatically andthe hydraulic system, including the control valve means, is shown insection.

Referrnig now to the drawing, an associated agricultural implement isconnected to a tractor by means of a pair of lower hitching links, oneof which is indicated by reference numeral 1, and an upper hitching link2. Lower links 1 are pivotally secured as at 3 to the tractor frame 4. Arockshaft 5 is connected by means of suitable linkage 6 to lowerlinks 1. Upper link 2 is pivotally secured to the torsion spring 7 whichin turn is anchored at S to the tractor frame. The torsion spring may beof the type disclosed in copending application Serial No. 76,903 filedDecember 19, 1960.

The position and draft control linkage 9 is shown diagrammatically. Itis similar to the differential linkage disclosed in detail in copeningapplication Serial No. 56,475 filed September 16, 1960, now Patent No.3,123,- 152, to which attention is invited. The members 10 and 11 arepivotally secured to torsion spring 7 and rockshaft 5, respectively, andtransmit forces therefrom to linkage 9. Position control lever 12 anddraft control lever 13 are connected by means of members 14 and 15,respectively, to linkage 9. Extending from linkage 9 is the operatingrod 16.

The control valve 17 includes housing 18 having therein the coaxialchambers 19, 2t and 21. A passage 22 communicates chamber 19 withchamber 20. A port defining the valve seat 23 communicates chamber 29with chamber 21. Housing 13 also includes the coaxial chambers 24 and25, the former communicating by means of the passage 26 with chamber 19.A port defining the valve seat 27 communicates chamber 24 with chamber25. The spaced ports 28 and 29 extend from chamber 19. The passage 313communicates chamber with chamber 19 through port 28.

Slidably received in chamber 19 is the valve spool 31 including thespaced lands 32, 33 and 34. The pin 35 extends from land 34 throughhousing 18 into chamber 20. Within chamber 21 is the check valve 36biased by means of the spring 37 toward valve seat 23. Operating rod 16extends through housing 18 into the chamber 19 and is engaged with land32 of valve spool 31. It is to be understood that suitable means forbiasing valve spool 31 may be provided.

The piston 38 is slidably received within chamber 24. Piston 38 hascontrol orifice 39 extending therethrough and the pin 40 projectingtherefrom. Within chamber 25 the check valve 41 is biased by means ofthe spring 42 toward valve seat 27.

The pump 43 is connected through the inlet line 44 with the reservoir45. The outlet line 46 of pump 43 communicates with chamber 25 inhousing 18 and through a pressure responsive relief valve with reservoir45. The lines 47 and 4S communicate chamber 24 and port 29,respectively, in housing 18 with reservoir 45.

with the hydraulic ram 50. This hydraulic ram 50 includes the cylinder51 and its associated piston 52 con-" nected by rneans of suitablelinkage 53 to rockshaft'S.

With control valve 17 in'the neutral position shown in the drawing,fluid passes from pump 43 through line 46 into chamber 25. A partialflow of fluid is established from chamber 25 through passage 30, port28, chamber 19 andwpassage 26 into chamber 24. Due to" the restrictionto flow through control orifice 39, a biasing 4 When link 2 senses areduction in the draft load on the implement a tension'force istransmitted therein which, after overcoming the resistance of torsionspring force is established which acts upon piston 38, thereby causingpin 40 to maintain, contact with check valve 41 and hold it away fromvale seat 27. The remaining fluid entering chamber 25 is bypassedthrough chamber 24 and line 47 back to reservoir 45. Check valve 36 'isseated against valve seat 23,thereby trapping fluid in cylinder 51.

For raising an associated implement, position control lever '12 is movedto one of itsraising positions. This movement is transmitted throughmember 14, linkage 9 and operating rod 16 to valve spool 31 whereuponvalve spool 31 is moved to the left, as shown in the drawing. Land 33clears the right side of port 28 and blocks the left side of port 28.Land 34 blocks port 29 entirely. Fluid trapped in chamber 24 abovepiston 38 bleeds through control orifice 39 at a predetermined rate. ingthus dissipated, check valve41 is seated on valve seat 27 whereupon-fullpump flow is applied from chamber 25 through passage 30, port 28,chamber 19 and passage 22 into chamber 20. Check valve 36 is moved offof valve seat 23 and fluid flows through chamber 21 and line 49 intocylinder 51 of hydraulic ram 50. Acting upon piston 52 it creates aforce which is transmitted through linkage53, rock-shaft .5 andlinkage-:6 to move' The biasingforce acting upon check valve 41 be--trol valve 17-to its neutral position once the imple- 'ment has attainedthe height predetermined by the setting of position control lever 12.

In order to drop the associated implement, position control lever 12 ismoved to one of its lowering positions'whereupon valve spool 31 is movedto the right. Pin35 engages and moves checkvalve' 36 oil of valve seat23 and land 34 clears port 29. Under the weight of the implement fluidflows from cylinder '51 through line 49, chamber 21, chamber 20, passage22, chamber 19, port 29 and line 48 to reservoir 45. Linkage 9'returnsmain control valve 17 to its neutral position when the associatedimplementhas been lowered to-a position corresponding to the setting ofpositioncontrol lever. 12.

The position of draft control lever 13 establishes a setting from whichan increase or decrease in draft load is effective for actuating thedraft compensating mechanism. When the draft load on the implementbecomes excessive a compressive force is transmitted through link 2 and,after overcoming 'the resistance of torsion spring 7, is furthertransmitted as a tension forcethrough member 10, linkage 9 and operatingrod 16 to valve spool 31 whereupon valve spool 31 is moved from theneutral position to the left. It is important to note that full pumpflow is applied. to cylinder '51 only after a delay determined by thetime required for fluid to bleed through control'orifice '39, afterwhich check valve sult in actuation of hydraulic'ram 50 to change theposition of links 1. Ratherphydraulic ram 50 is actuated to change thedraft only when a true variation in draft load is sensed by link 2.

7, is further transmitted asa compressive force through member 10,linkage 9 and operating rod 16 to valve spool 31 whereupon valve spool31 is moved from the ';neutral' positionto the right and fluidisrelieved from cylinder 51.1, The implement dropped and control valve17 is returned to its neutral position under the influence of linkage 9.If at this point the draft load on the implement is momentarilyexcessive, valve spool 31 will again be moved to the left.Over-compensation is avoided, however, because of the delay in applyingfull pump pressure to, hydraulic ram 50 after movement of valve spool31to the left.v

At all times fluidpressure in the system. remains at or below the valuerequired for actuation of hydraulic ram 50. This avoids-overheating ofthe fluid and resultant damage to hydraulic system components.

An additional fail-safe feature incorporated herein is provided by thearrangement-which insures that fluid will be bypassed to reservoir inthe event that control orifice 35! becomes clogged. In such an eventfluid trapped in chamber 24 will insure that check valve 41 ismaintained in a position away from its associatedvalve seat 27. Thisfeature also provides insurance against overheating of the fluid in'thesystem.

It is to be understood that the foregoing description and theaccompanying drawing have been given only by 30 way of illustration andexample. Changes in the elements, rearrangement'of parts, andsubstitution of equivalents, all of which will be obvious to thoseskilled in the art; are considered to be within the scope of the presentinvention which is limited only by the claims which follow.

What is claimedis: V

-1. For use with a tractor and an implement hitched to said tractor;power means including fluid operated ram meansfor moving said implementbetween transport and work positions and for controlling the draft.thereof when in said workposition; means for selectively regulating theflow of fluid to and from said ram means for respectively raising andlowering said implement; manually operable means for actuating saidregulating means; sensing means responsive to variations in thedraftload on 'said implement for actuating said regulating means;saidregulatingmeans including an inlet line connected to a source offluid under pressure, a control line connected in said ram means,anexhaust line, control valve means selectively movablefrom a neutralposition to first and second actuating positions communicating saidinlet line with said control line and said control line with saidexhaust line, respectively, unloading-valve means movable between afirst position communicating said inlet line with said exhaust line anda second position blocking communicationof said'inlet line with saidexhaust line, and fluid pressure responsive means communicating withsaid source of'fiuid under pressure through said control valve meanswhen said control valve means is in said neutral position for biasingsaid unloading valve means toward itsfirst position when said controlvalve means is in said'neutral position and for a'p'redetermined timeupon movement of said control valve means from said neutral position tosaid first actuating position.

2. Fluid flow regulating means comprising an inlet line adaptedto beconnected to a source of fluid under pressure, a control line adapted tobe connected to a fluid pressure operated device, an exhaust line,dashpot means having a relatively large inlet and a relatively smalloutlet communicating with'said exhaust line, control valve means movablebetween a neutral position communicating said inlet line with said inletof said dashpot means, a first actuating position blocking communicationof said inlet line withsaid' inlet of said dashpot meansandcommunicating said inlet 'line with said control line, and a secondactuating position communicating said control line with said exhaustline, and unloading valve means movable between a first positioncommunicating said inlet line with said exhaust line and a secondposition blocking communication of said inlet line with said exhaustline, said dashpot means having means responsive to fluid pressure insaid inlet of said dashpot means for biasing said unloading valve meanstoward its first position.

3. For use with a tractor and an implement hitched to said tractor;power means including fluid operated ram means for moving said implementbetween transport and work positions and for controlling the draftthereof when in said work position; means for selectively regulating theflow of fluid to and from said ram means for respectively raising andlowering said implement; manually operable means for actuating saidregulating means; sensing means responsive to variations in the draftload on said imple ment for actuating said regulating means; saidregulating means including an inlet line connected to a source of fluidunder pressure, a control line connected to said ram means, an exhaustline, dashpot means having a relatively large inlet and a relativelysmall outlet communicating with said exhaust line, control valve meansmovable between a neutral position communicating said inlet line withsaid inlet of said dashpot means and first and second actuatingpositions communicating said inlet line with said control line and saidcontrol line with said exhaust; line, respectively, unloading valvemeans movable between a first position communicating said inlet linewith said exhaust line and a second position blocking communication ofsaid inlet line with said exhaust line, and means biasing said unloadingvalve means toward its second position, said dashpot means having meansresponsive to fluid pressure in said inlet of said dashpot means foroverriding said biasing means and holding said unloading valve means inits first position when said control valve means is in said neutralposition, said biasing means being sufiicient to override said fluidpressure responsive means upon relief of fluid pressure through saidoutlet of said dashpot means when said control valve means is moved fromsaid neutral actuating position.

4. For use with a tractor and an implement hitched to said tractor;power means including fluid operated ram means on said tractor formoving said implement between transport and work positions and forcontrolling the draft thereof when in said work position; means forselectively regulating the flow of fluid to and from said ram means forrespectively raising and lowering said implement; manually operablemeans for actuating said regulating means; and sensing means responsiveto variations in the draft load on said implement for actuating saidregulating means; said regulating means including an inlet lineconnected to a source of fluid under pressure, a control line connectedto said ram means, an exhaust line, dashpot means having a relativelylarge inlet and a relatively small outlet communicating with saidexhaust line, control valve means movable between a neutral positioncommunicating said inlet line with said inlet of said dashpot means andfirst and second actuating positions communicating said inlet line withsaid control line and said control line with said exhaust line,respectively, unloading valve means movable between a first positioncommunicating said inlet line with said exhaust line and a secondposition blocking communication of said inlet line with said exhaustline, and means biasing said unloading valve means toward its secondposition, said dashp-ot means having piston means responsive to fluidpressure in said inlet of said dashpot means for overriding said biasingmeans and holding said unloading valve means in its first position whensaid control valve means is in said neutral position, said biasing meansbeing sufiicient to override said fluid pressure responsive piston meansupon relief of fluid pressure through said outlet of said dashpot meanswhen said control valve means is in said first actuating position.

5. In the invention according to claim 4, said outlet of said dashpotmeans being an orifice extending through said piston means.

6. The invention according to claim 4, further comprising fluid pressureresponsive check valve means in said control line movable between afirst position communicating said control line with said ram means and asecond position blocking communication of said control line with saidram means, and means associated with said control valve means forholding said check valve means in its first position when said controlvalve means is in said second actuating position.

7. Fluid flow regulating means comprising an inlet line adapted to beconnected to a source of fluid under pressure, at least one control lineadapted to be connected to a fluid pressure operated device, an exhaustline, dash pot means having a relatively large inlet and a relativelysmall outlet communicating with said exhaust line, control valve meansmovable between a neutral position communicating said inlet line withsaid inlet of said dashpot means and a plurality of actuating positionsselectively communicating said inlet line with said control and exhaustlines, unloading valve means movable between a first positioncommunicating said inlet line with said exhaust line and a secondposition blocking communi cation of said inlet line with said exhaustline, and means biasing said unloading valve means toward its secondposition, said dashpot means having means responsive to fiuid pressurefor overriding said biasing means and holding said unloading valve meansin its first position when said control valve means is in said neutralposition, said biasing means being sutficient to override said fluidpressure responsive means upon relief of fluid pressure through saidoutlet of said dashpot means when said control valve means is in atleast one of said actuating positions.

References tilted by the Examiner UNITED STATES PATENTS ABRAHAM G.STONE, Primary Examiner.

T. GRAHAM CRAVER, Examiner.

1. FOR USE WITH A TRACTOR AND AN IMPLEMENT HITCHED TO SAID TRACTOR;POWER MEANS INCLUDING FLUID OPERATED RAM MEANS FOR MOVING AND IMPLEMENTBETWEEN TRANSPORT AND WORK POSITIONS AND FOR CONTROLLING THE DRAFTTHEREOF WHEN IN SAID WORK POSITION; MEANS FOR SELECTIVELY REGULATING THEFLOW OF FLUID TO AND FROM SAID RAM MEANS FOR RESPECTIVELY RAISING ANDLOWERING SAID IMPELEMENT; MANUALLY OPERABLE MEANS FOR ACTUATING SAIDREGULATING MEANS; SENSING MEANS RESPONSIVE TO VARIATIONS IN THE DRAFTLOAD ON SAID IMPLEMENT FOR ACTUATING SAID REGULATING MEANS; SAIDREGULATING MEANS INCLUDING AN INLET LINE CONNECTED TO A SOURCE OF FLUIDUNDER PRESSURE, A CONTROL LINE CONNECTED TO SAID RAM MEANS, AN EXHAUSTLINE, CONTROL VALVE MEANS SELECTIVELY MOVABLE FROM A NEUTRAL POSITION TOFIRST AND SECOND ACTUATING POSITIONS COMMUNICATING SAID INLET LINE WITHSAID CONTROL LINE AND SAID CONTROL LINE WITH SAID EXHAUST LINE,RESPECTIVELY, UNLOADING VALVE MEANS MOVABLE BETWEEN A FIRST POSITIONCOMMUNICATING SAID INLET LINE WITH SAID EXHAUST LINE AND A SECONDPOSITION BLOCKING COMMUNICATION OF SAID INLET LINE WITH SAID EXHAUSTLINE, AND FLUID PRESSURE RESPONSIVE MEANS COMMUNICATING WITH SAID SOURCEOF FLUID UNDER PRESSURE THROUGH SAID CONTROL VALVE MEANS WHEN SAIDCONTROL VALVE MEANS IS IN SAID NEUTRAL POSITION FOR BIASING SAIDUNLOADING VALVE MEANS TOWARD ITS FIRST POSITION WHEN SAID CONTROL VALVEMEANS IS IN SAID NEUTRAL POSITION AND FOR A PREDETERMINED TIME UPONMOVEMENT OF SAID CONTROL VALVE MEANS FROM SAID NEUTRAL POSITION TO SAIDFIRST ACTUATING POSITION.